Gas heater



Aug. 2, 1966 K. oEcHsLlN ETAL 3,263,572

GAS HEATER Filed April 1e, 1965 NVENTCRS KONRAD OEC HsLlN PAUL Mesi-:F2

@Y @MP We@ ATTORNE YS United States Patent O 3,263,672 GAS HEATER Konrad Oechslin, Zurich, and Paul Moser, Winterthur,

Switzerland, assigner-s to Escher Wyss Aktiengesellchft, Zurich, Switzerland, a corporation of Switzer- Filed Apr. 16, 1965, Ser. No. 448,591 Claims priority, application Switzerland, May 28, 1964, 6,972/64 Claims. (Cl. 126-109) This invention relates to a tubular gas heater, more particularly for thermal power plants operating with a closed circuit of a gaseous working medium, having a radiation part with vertical heater tubes, which terminate at one end in an immovable horizontal header, carrying the entire stream of working medium, and which open at the other end into a number of horizontal partial headers, carrying only part of the working medium. The partial headers are movable in the direction of the heater tube axis, are approximately compensated for weight by `simple means, such as weights or springs, and are tlexibly connected to an immovable working-medium supply source.

In thermal power plants of the kind specified, the working medium, as a rule, is heated to 750 C. and above, which makes it necessary lto use in the heater part tubes consisting of austenitic material, which expand considerably at the prevailing temperatures. To ensure the taut condition and straight shape of the heater tubes, the latter are inserted at one end in an immovable header, and at their other end are flexibly connected to the respective associated part of the plant. Since it is desired `to have the shortest possible connecting pipeline between the radiation part of the heater and Ithe thermal power machine of the thermal power plant, the working medium outlet of the radiation part is situated on the immovable heater tube header -arranged at the base of the combustion chamber, and the upper ends of the heater tubes are flexibly connected to the immovable working medium outlet of the convection part of the heater.

Diiculties have always been encountered in allowing all the heater tubes to open into a common upper mov- -able header. Even if the arrangement of the heater tubes approximates as'closely as possible to a circular form, resulting in substantially equal distance of the heater tubes from the flame axis, it is impossible in practice, particularly in the case of powdeerd coal tiring, to avoid displacement of the llames and hence the formation of gas strands at different tempreatures. Additional dificulties of this kind arise when a number of burners are used, or in the case of partial load operation using part of a number of burners. The effect of these conditions is that heater tubes, which in particular are comparatively remote from each other, may have greatly different wall temperatures, resulting in extremely different expansion-s of such tubes. In such cases, with a single common header, the coldest heater tubes would be subjected to inadmissably high compressive stresses, and the hottest heater tubes would be exposed to corresponding tensile stresses.

In known heaters, this drawback is obviated by arranging for a number of adjacent heater tubes to open into one of a number of movable partial headers. Thus, for example, a heater is known having a radiation part of octagonal outline in plan and having eight movable upper partial headers. The connections between the movable partial headers and the immovable working medium outlet of `the convection part, which connections must also take up variations in the axial directions of the partial headers in relation to each other, consists of four per partial header, atotal of lthirty-two, exible coil-shaped connecting pipes of a length exceeding by a multiple the shortest distance between the points to be connected. These combined measures afford the necessary flexibility'. However, this construction has the great drawback that scarcely two connecting pipes have the same length and form, so that at each transition from a connecting pipe to a partial header, different working pressures prevail. Therefore there are different quantities of Working medium in the individual heater tubes. This leads to an additional greater expansion of the heater tube concerned when a smaller current of working medium comes into contact with more intense flame-side heating. Furthermore, the connection of the many connecting pipes to the parti-al headers and to the headers opening into the Working medium outlet of the convection part is expensive, and renders diticult the supervision and maintenance of the many connecting pipes, particularly where they run close to one another. The iiexible support and thermal insulation of the many connecting pipe-s is complicated, as is their ilexible passage through the walls of the thermally insulating housing surrounding the partial headers.

It is an aim of the invention to obviate these drawbacks. For this purpose, :a radiation and convection heater of the hereinbefore described kind is constructed `according to the invention such that there is provided a horizontal header carrying the entire working medium stream, movable in the direction of the heater tube axis and connected by flexible connections to the partial headers, and which is connected to the Working medium outlet of the convection part by at least one llexible connecting pipe. Moreover, the heater is provided with a measuring device, measuring the relative position of the movable header with regard to one or more of the partial headers, and with an adjusting device for the movable header.

A constructional example of the invention is represented in simplied form in the drawing, the single figure of which shows a radiation and convection heater in vertical section. v

The heater has the vertical radiation part 1 and the convection part 2. Vertical heater tubes 4 of austenitic material, extending near the inner :surface of the cylindrical combustion chamber Wall 3, are provided in the radiation part 1. Above the combustion chamber is a thermally insulating housing 6, reinforced by supporting walls 5. At the base of the radiation part 1, below the combustion chamber, all the heater tubes 4 open into an immovable horizontal annular header 7, carrying the entire working medium stream and provided with the working medium outlet 8, from which a working medium pipeline, not shown, leads to a thermal power machine, not shown. In the roof of the combustion chamber are four burners 9, of which only two are -visible. Above the combustion chamber an equal number of heater tubes 4 open respectively into four, horizontal, annular sector-formed partial headers 10, of which only one is shown entirely and two partly. These headers, e-ach of which carries only part of the working medium stream, are movable in the direction of the heater tube axis and are situated in the lower region of the housing 6. Mounted in the roof of the housing 6 are brackets 11, in which are pivoted two-armed levers 12. Each shorter lever arm is connected by a yoke 13 to a partial header 10, while each longer arm carries a weight 15 by means of a rod 14, the partial headers being thereby approximately compensated for weight. Only one such compensating device is shown in the drawing.

The convection part 2, which is connected to the radiation part 1 by a length of flue 16, has a working medium inlet 17, .a heater tube coil system 18 and an immovable working medium outlet 19.

Situated in the housing 6 above the partial headers 10 isa horizontal annular header 21 carrying the entire working medium stream, movable in the direction of the heater tube axis, vertically flush with the partial headers 10, and

connected to the latter respectively by flexible, bellowstype connections 20 parallel to the header tube axis and arranged in the region of the associated yoke 13. Coaxial with these connections 20 and corresponding to them, blind connections 22 lead from the top of the movable header 21 to the upper horizontal beams of the yokes 13, the interior of the blind connections 22 being in communication with the interior of the movable header 21, and the blind connections 22 being closed at the top. Mounted in the roof of the housing 6 are brackets 23, in which .are pivoted two-armed levers 24. Each shorter lever arm is connected `by a connecting rod 25 to the movable header 21, while each longer lever arm carries a weight 27 by means of a connecting rod 26, the movable header 21 being thereby approximately compensated for weight. In the drawing, only one such compensating device is shown.

The movable header 21 is connected to the working medium outlet 19 of the convection part 2 by means of two symmetrical connecting pipes 28, which on the Whole `are liexible and of which only one is visible. Each connecting pipe 28 has ya vertical member 29 and a horizontal member 30, in which are interposed two bellows-type pipe lengths 31, 32.

The upper horizontal beam of the yoke 13 shown is formed as a portion of a rod 33, which is led to the exterior through a vertical slit 34 in the wall of the housing 6. In the reach of said yoke 13, the movable header 21 carries a horizontal rod 35 parallel to the rod 33 land situated vertically below it, which rod 35 passes to the exterior through a vertical slit 36. The rods 33, 35 are connected to `a measuring device 37, which measures their distance apart and hence the relative position `of the movable header 21 with regard to one of the partial headers 10, and which is so constructed 4that on deviation of the said relative position from a range of predetermined width in either direction, a control force, corresponding to the direction of the deviation, is produced. The measuring device 37 is connected by a control line 38 to a control ydevice 39. In its turn, the control device 39 is connected by a power line 40 to a source of power, not shown, and also by means of a servo-line 41 to a servomotor 42 producing a rotary movement in one direction or the other.

According to the representation of the drawing, the measuring device 37 has two contacts 43, 44, fast with the rod 35, and a Contact 4S, fast with the rod 33, whereby electrical control forces are initiated. Advantageously, the servomotor 42 is in the form of a reversible electric motor. Of course, any other type of construction may be used as measuring device, control device and servomotor.

The rot-ating shaft 46 of the servomotor 42 carries on its free end a bevel pinion 47 meshing with a vertical axis bevel gearwheel 48, which is fast for movement in the axial direction, and the hub of which has an internal screw thread receiving a screw threaded spindle 49, which is fast for rotation, but is movable in the direction of the bevel gearwheel axis. The screw threaded spindle 49 is connected by a rod 50 and two joints 51 and 52 to the inner end of the horizontal member 30 of the connecting pipe 28. The servomotor 42, the bevel gearings, yand screw threaded spindles form the essential parts of an adjusting device for the movable header 21.

The plant shown operates as follows. During firing of the combustion chamber, the heater tubes 4 of austenitic material, which carry the working medium in its hottest state, expand considerably; the expansion being much greater than that of the vertical members 29 of the connecting pipes 28, which are made of ferritic material, and in which the working medium has a lower temperature. In a constructed plant, the difference in expansion amounts to 60 mm.

Since the lower header 7 is immovable, the partial headers are moved upwardly, corresponding to the thermal expansion of the heater tubes 4, different expansions of the individual heater tubes 4, owing to the un- `symmetrical llames, producin-g different movements of the individual partial headers 10 in the direction of the heating tube axis, and/or different axial d-irection trends of the partial headers 10 .in relation to each other. The movements of each of the partial headers 10 act on the movable header 21 through the associated connections 20 and corresponding blind connections 22 and yokes 13. Different movements and/ or different axial direction trends of the individual partial headers 10 will be compensated by the connections 20 and blind connections 22 in that the average Iof all the movements of the partial headers 10 willl act on the movable header 21. Due to this, and also in consequence 0f the symmetrical connection of the two symmetrical connecting pipes 28 to the movable header 21, the latter maintains in all positions substantially its horizontal axial direction. Since in the inside of each blind connection 22, working medium is present 'at the same temperature as in the interior of each associated connection 20, the thermal expansion moments of the connection 20 will be compensated by corresponding moments of the blind connections 22.

The weight-compensated partial headers 10 can move upwardly as such, on thermal expansion of the heater tubes 4, against negligibly slight resistance. The movable header 21 is Weight compensated, including the part ofthe weight of the connecting pipes 28 and connections 20 and blind connections 22 acting on it. It can, however, be moved in the axial direction, that is to say up wardly, in thermal expansion of the heater tubes 4, only by overcoming considerable resistances. These are the frictional resistances of the connecting pipes 28 in their passage through the wall of the thermally `insulating housing 6, and the deformation resistances in the bellows-type, flexible pipe lengths 31 and 32 in the horizontal members of the connecting pipes 28. Due to this resistance against displacement of the movable header 21, the latter either does not follow the upward movement of partial headers 10, or follows this movement only partially or with delay. Consequently, when the partial headers 10 move upward, :the connections 20 will be compressed and the blind connections 22 extended, thereby altering the relative position of the movable header 21 in relation to the partial headers 10. As a result, the spacing between rod 33 and rod 35 increases. Consequently, the contact 45 comes into contact with the contact 44 of the measuring device 37, whereby the control device 39 is operated in the sense that servo-energy is supplied to the servomotor 42 and causes the motor shaft 46 to rotate in that direction in which the movable header 21 is moved upwardly by the vertical member 29 of the connecting pipe 28. When the predetermined relative position between the movable header 21 and the partial headers 10, and hence the predetermined spacing between rod 33 and rod 35, is reestabl-ished, contact between the contacts 44, 45 is broken, and the supply of energy to the servomotor 42 is interrupted. When, owing to cooling, the heating tubes contract, the contact 45 contacts the contact 43 and brings about the Ilowering of `the movable header 21.

Due to the measures according to the invention, it is possible to supply the working medium to the radiation part of a radiation and convection heater in such a manner that the same working medium pressure prevails in eac-h movable partial header, and that the same quantity of working medium flows in all the heater tubes. The yinvention also reduces the number of lexible connecting pipes between the convection and radiation parts. A further advantage of the plant shown is that the expansion of the heater tubes is used as a control quantity, and the adjustment of the movable header is effected by an extraneous force, so that the heater tubes are always directed straight in a positive manner and are not subjected to any compressive stresses.

In the plant shown, the measuring device picks up the position of only one partial header. To obtain a measured result based on the mean position of all the partial headers, it will be necessary, for example, to provide each partial header with its own measuring device, the cont-rol device taking care of compensation, or each partial header may be connected to a compensating device, transmitting the mean position of the partial header to the control device.

In an -alternative construction, the two vertical rods of the yoke 13 are replaced by one rod which passes through the interior of the connection 20 and of the associated blind `connection 22. This embodiment has the advantage that the internal rod has the same temperature as the two connections, and the thermal expansion of these connections corresponds approximately to the thermal expansion of theinternal rod. As a result, loading of the connections, corresponding to the thermal expansion, is obviated.

If the Weight-:compensating devices for the movable header an-d the partial headers are correctly designed, the necessary adjustment forces are not particularly lange. It is therefore quite feasible to provide an adjusting device operated directly by hand. Such a manual adjusting device lwill be provided advantageously as an auxiliary adjusting device in the event of failure of the automat-ic adjusting device. Furthermore, provision will advantarg ously be made for the power-operated adjusting device to be disconnected on connecting the manual adjusting device. This may be done, for instance, by alternately coupling the engagement and disengagement devices of the two adjusting devices with each other. A particularly reliable disengagement of the power-operated adjusting device is obtained if the electric servomotor is in the form of a sliding armature motor, the driving shaft of which is moved into the engagement position only on the supply or delivery of power. In the event of failure of the power-operated adjusting device, the latter is always disconnected. The necessity for operating the manual adjusting device will advantageously be indicated by an insistently operating Warning device, for example an acoustic warning device, which is driven by a device, such as a spring or a weight, that reliably stores up force without special expenditure and is controlled by the rods 33, 35.

What is claimed is:

1. A-tubular heater for heating the gaseous working medium of a closed-circuit gas turbine plant by heating gases comprising in combination wal-ls confining a heating chamber for the throughllow of said heating gases and vertical heater tubes exposed to the heating gases in said chamber dening a ow .path for said working medium; and immovable horizontal header, said vertical heater tubes terminating at one end in said header, the same carrying the entire stream of the working medium; a number of partial headers movable in the direction of the axis of said heater tubes, the same terminating at the other end in said partial hea-ders, each of same carrying -only part of the stream of the working medium; `a horizontal header movable in the direction of the axis of said heater tubes; a number of flexible connections connecting said partial headers with said movable header, the same carrying the entire stream of the working medium; the number of flexible connections being at least equal to the number of said partial headers; at least one flexible supply pipe having a fixed end and a movable end terminating in said movable header; a measuring device for measuring the relative position of said movable header to one or more partial headers; and an adjust-ing device `for said movable header.

2. The combination dened in claim 1 in which the number of exible supply pipes is inferior to the number of the partial headers.

3. The combination defined in claim 2 having two liexible supply pipes which are symmetrical with respect to a plane passing through the axis of the heating chamber.

4. The combination defined in claim 1 having a control device and a servomotor serving as adjusting device, said control device being connected with the measuring device and with said servomotor in such a manner that the relative position of the movable header to the partial headers remains substantially the same.

5. The combination defined in claim 1 in which the movable header is arranged in the vicinity of the partial headers and is substantially in alignment with the latter ver-tically.

6. The combination defined in claim 1 having a thermally insulating housing adjacent the heat-ing chamber, the partial headers and the movable header being placed in said housing.

7. The combination defined in claim 1 having devices generating upward directed forces connected with the partial headers so as to compensate the weights of said partial headers approximately.

8. The combination defined in claim 1 having a device generating an upward directed force connected with the movable hea-der so as to -compensate the weight of said movable header approximately.

9. The combination defined in claim 1 having blind flexible connections arranged ico-axially with the flexible connections on the side of the movable header remote from the partial headers, the interior of said blind flexible connections communicating with the interior of said movable header, and having holding devices fixed at one end on said partial headers and at the other end on the blind closed ends 4of said blind flexible connections so as to hold said blind closed lends of said blind ilexible connections -in a iixed position in relation to the associated partial header.

10. A heater for heating the gaseous working medium of a closed-circuit gas turbine plant by combustion gases, said heater comprising in combination .a radiation part having walls confining a radiation heating chamber of circular horizontal projection with burner means causing combustion of fuel arranged at the top of said radiation heating chamber, the same being throughflown by the combustion gases condescendingly, and having vertical radiation heater tubes exposed to the radiant heat of the combustion gases in said radiation heater chamber, said radiation heater tubes being circularly arranged in said radiation heating chamber so as to encircle the stream of said combustion gases; an immovable horizontal annular header placed underneath the radiation heating chamber adjacent the same, the radiation heater tubes penetrating the bottom wall of the radiation heating chamber and terminating in said immovable header, the same carrying the entire stream of the working medium; an outlet pipe for the working medium being connected with said immovable header; a thermally insulating housing arranged above the radiation heating chamber so as to encircle said burner means; four partial horizontal headers of ring segment form disposed in said housing movable in the direction Iof the axis of the radiation heater tubes, the same penetrating the cover wall of the radiation heating chamber and terminating in said partial headers, each of same carrying only part of the stream of the Working medium; a horizontal annular header movable in the direction of the axis of the radiation heater tubes; four ilexible connections each connecting one of said partial headers with said movable header, the latter carrying the entire stream of the working medium and being in alignment with said partial headers vertically, and the flexible connections being arranged co-axially with the axis of the radiation heater tubes; four blind flexible connections arranged co-axially with :the flexible connections on the side of the movable header remote from the partial headers, the interior of said blind ilexible connections communieating with the interior of the movable header; four holding devices, each fixed `at one end on one of the partial headers an-d at :the other end on the blind closed ends of one of said blind |flexible connections so as to hold said blind closed ends of said blind llexibl-e connections in a fixed position in relation to the associated partial header; and counter Weights with shift levers for compensating the Weights of the movable header and the partial headers approximately; a convection part having Walls conning a convection heating chamber arranged near the radiation part, the former being throughown by t-he combustion ygases upwards; an horizontal joint means connecting "the outlet for the combustion ygases of the radiation heating chamber with the inlet for the combustion gases of the convection heating chamber; said convection part having a convection heating tube system exposed to the combustion Vgases in said chamber conning a ow -pat-h for the working medium, said tube system having an inlet co1- lecting pipe and an outlet collecting pipe both immovable; two symmetric ilexible supply pipes connecting the working medium outlet pipe of the convection part with the movable header, said exible supply pipes penetratin-g the wall of the thermally insulating housing; a measuring device measuring the relative position of the movable header to a partial header; a control device and a servomotor serving as adjustment device for the movabile header, said control device being connected with said measuring device and with said servomotor in such a manner that the relative position of the movable header to the partial headers remains substantially the same.

References Cited by the Examiner UNITED STATES PATENTS 2,524,637 10/1950 Ruegg 126l09 JAMES W. WESTHAVER, Primary Examiner. 

1. A TUBULAR HEATER FOR HEATING THE GASEOUS WORKING MEDIUM OF A CLOSED-CIRCUIT GAS TURBINE PLANT BY HEATING GASES COMPRISING IN COMBINATION WALLS CONFINING A HEATING CHAMBER FOR THE THROUGHFLOW OF SAID HEATING GASES AND VERTICAL HEATER TUBES EXPOSED TO THE HEATING GASES IN SAID CHAMBER DEFINING A FLOW PATH FOR SAID WORKING MEDIUM; AND IMMOVABLE HORIZONTAL HEADER, SAID VERTICAL HEATER TUBES TERMINATING AT ONE END IN SAID HEADER, THE SAME CARRYING THE ENTIRE STREAM OF THE WORKING MEDIUM; A NUMBER OF PARTIAL HEADERS MOVABLE IN THE DIRECTION OF THE AXIS OF SAID HEATER TUBES, THE SAME TERMINATING AT THE OTHER END IN SAID PARTIAL HEADERS, EACH OF SAME CARRYING ONLY PART OF THE STREAM OF THE WORKING MEDIUM; A HORIZONTAL HEADER MOVABLE IN THE DIRECTION OF THE AXIS OF SAID HEATER TUBES; A NUMBER OF FLEXIBLE CONNECTIONS CONNECTING SAID PARTIAL HEADERS WITH SAID MOVABLE HEADER, THE SAME CARRYING THE ENTIRE STREAM OF THE WORKING MEDIUM; THE NUMBER OF FLEXIBLE CONNECTIONS BEING AT LEAST EQUAL TO THE NUMBER OF SAID PARTIAL HEADERS; AT LEAST ONE FLEXIBLE SUPPLY PIPE HAVING A FIXED END AND A MOVABLE END TERMINATING IN SAID MOVABLE HEADER; A MEASURING DEVICE FOR MEASURING THE RELATIVE POSITION OF SAID MOVABLE HEADER TO ONE OR MORE PARTIAL HEADERS; AND AN ADJUSTING DEVICE FOR SAID MOVABLE HEADER. 